Dylan Hutchison created SYSTEMML-1985:
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Summary: Sparsity estimates of constant multiply
Key: SYSTEMML-1985
URL: https://issues.apache.org/jira/browse/SYSTEMML-1985
Project: SystemML
Issue Type: Improvement
Reporter: Dylan Hutchison
Priority: Minor
I've seen the following in the output of Explain recompile_hops:
{noformat}
--(505) TRead HV [327,1,1000,1000,327] [0,0,0 -> 0MB], CP
--(37959) b(*) (505,[-0.0053168...]) [327,1,1000,1000,-1] [0,0,0 -> 0MB], CP
{noformat}
The nnz of Hop 37959 here is 327, because multiplying a matrix by a non-zero
constant does not change the non-zero structure. But the current code marks
the nnz as -1 (unknown nnz).
Let's add a check to the {{refreshSizeInformation}} of BinaryOp to handle this
and related cases like division by a nonzero.
Addition, subtraction, and mod might create zeros so they are tricky; however
we can upper bound their nnz. Maybe this might be helpful in a different place?
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